1. Field of the Invention
The present invention relates to a field emission display (FED) and more particularly, to a spacer discharging apparatus and method of a field emission display (FED).
2. Description of the Background Art
In general, as the information processing systems are developed and widely spread, a display device as a time information transmission means has increasing importance. Of display devices, researches are actively ongoing on a flat panel display such as a liquid crystal display (LCD), a plasma display panel (PDP) and the FED or the like, to accomplish a large screen, flatness, high luminance and high efficiency.
Especially, the FED, which is anticipated to be commercialized in the near future, receives much attention as a flat panel display for a next-generation information communications, which overcomes shortcomings of the flat display devices.
The FED includes a front substrate having a fluorescent material and an anode electrode and a back substrate having a gate electrode and a cathode electrode. In the FED, the distance between the front substrate and the back substrate is approximately 1˜2 mm, short, so a high electric field is formed by a high voltage applied to the anode electrode. Accordingly, in the FED, electrons discharged by a difference between voltages applied to the gate electrode and the cathode electrode formed on the back substrate are drawn by the electric field formed by the high voltage-applied anode electrode, to excite the fluorescent material so as to be emitted.
The construction of the FED in accordance with the conventional art will now be described with reference to FIG. 1.
FIG. 1 is a sectional view showing the construction of the FED in accordance with the conventional art.
As shown in FIG. 1, the conventional FED includes a back substrate 110 having a cathode electrode 107, a dielectric layer 106 and a gate electrode 105 sequentially stacked on a lower glass substrate 108; and a front substrate 100 having an anode electrode 102 and a phosphor 103 sequentially stacked on an upper glass substrate 101.
A spacer 104 is positioned between the upper glass substrate 101 and the lower glass substrate 108 to maintain a certain distance therebetween. In addition, spacers 104 are distributively and evenly positioned on the entire surface of the front substrate 100 and the back substrate 110 so as to sufficiently tolerate a difference between an external atmospheric pressure and an atmospheric pressure according to high vacuum at the inner side thereof.
The conventional FED operates as follows.
First, when a certain voltage is applied to the gate electrode 105 and the cathode electrode 107, electrons are discharged from the cathode electrode 107 and the discharged electrons passes through the gate electrode 105 so as to be discharged by a quantum-mechanical tunneling effect. At this time, if the applied voltage is relatively high, the amount of electrons discharged from the cathode electrode 107 is increased, while if the applied voltage is relatively low, the amount of electrons discharged from the cathode electrode 107 is decreased.
Thereafter, the electrons discharged from the cathode electrode 107 are accelerated toward the anode electrode 102 with the phosphor 103 coated thereon by being influenced by the electric field formed by the high voltage applied to the anode electrode 102. Accordingly, electrons collide with the phosphor 103 to generate energy.
Electrons existing in the phosphor 103 are excited by the generated energy to emit visible light.
However, some of electrons discharged from the cathode electrode 107 are not accelerated toward the phosphor-coated anode electrode 102 but collide with the spacer 104 to electrostatically charge the surface of the spacer 104. Namely, the charged electrons can change distribution of a voltage around the spacer 104. In this case, since the change in the voltage distribution around the spacer 104 can distort flow of the discharged electrons, causing degradation of a display state such as appearance of noise on the screen and visible appearance of a position of the spacer 104 on the screen. In addition, the change in the voltage distribution around the spacer 104 can generate an electric arc between the spacer 104 and the cathode electrode 107.
FIG. 2 is a plan view showing the structure of the FED in accordance with the conventional art.
As shown in FIG. 2, the conventional FED includes a scan electrode 107A applying a scan voltage to the cathode electrode 107; a data electrode 105A applying a data voltage to the gate electrode 105; and a high voltage power source unit 200 applying a high voltage to the anode electrode 102.
The conventional FED constructed as described above operates as follows.
First, a high voltage is applied from the high voltage power source unit 200 to the anode electrode 102. And, a scan voltage is applied to the scan electrode. 107A and a data voltage is applied to the data electrode 105A.
The applied scan voltage and the data voltage are respectively applied in synchronization with each other to the scan electrode 107A and the data electrode 105A, so that pixels are selected and driven to display an image on a screen.
However, the conventional FED does not have a discharge path for discharging electric charge charged on the spacer 104, so a noise is generated with the image displayed on the screen for a certain time while the electric charge charged on the spacer 104 is being discharged. This will now be described with reference to FIG. 3.
FIG. 3 is a graph showing a change of a voltage applied to an anode electrode of the FED in accordance with the conventional art.
As shown in FIG. 3, the change of the voltage applied to the anode electrode of the conventional FED indicates that even after the high voltage applied to the anode electrode 102 is cut off or power applied to the scan electrode 107A is cut off, the voltage or the power is gradually reduced for a certain time, so that there is a high possibility that noise generated on the screen.
In order to solve such a problem, a spacer discharging apparatus of the conventional FED in which a ground electrode is formed at a lower end portion of the spacer 104 will now be described with reference to FIG. 4.
FIG. 4 is a plan view showing the spacer discharging apparatus of the FED in accordance with the conventional art.
As shown in FIG. 4, the spacer discharging apparatus of the conventional FED includes a spacer ground electrode 104A formed at a lower end portion of the spacer 104.
However, even though the spacer ground electrode 104A is formed at the lower end portion of the spacer 104 to discharge electric charge charged at the spacer 104, the electric charge is not quickly discharged from the spacer 104 and the spacer 104 is radiated for a certain time.
As mentioned above, the conventional FED has the following problems. That is, since the electrons discharged from the cathode electrode collide with and are accumulated in the spacer, noise is generated on the screen.